Synthesis and characterization of fluorinated polyimides derived from novel unsymmetrical diamines

Thermal and oxidative behavior of a tetraphenylsilane-containing phthalonitrile polymer

Phthalonitrile polymers have potential for high-temperature applications in polymer matrix composites as electronic encapsulation compounds. To investigate the effect of inclusion of an organosilicon moiety, a tetraphenylsilane-containing phthalonitrile monomer was synthesized in high yields. The monomer possessed a high melting point of 222–223°C, while no hydrolytic sensitivity was observed. Cured polymers exhibited glass transitions in the range of 290–325°C and coefficients of thermal expansion of 73–77 µm/(m °C). In thermogravimetric analysis (TGA), 5 wt% loss was observed at 482–497°C and 519–526°C, under air and nitrogen, respectively. Infrared (IR)-TGA of evolved gases revealed multiple degradations in both nitrogen and air. The material possessed good thermo-oxidative stability (TOS) when aged in air at 250°C. After aging for 5000 h, oxidative degradation was characterized using Fourier transform IR microscopy, energy dispersive spectroscopy, optical microscopy, and Knoop hardness testing. Four zones were identified in aged samples. The cleavage of Si-phenyl bonds and the formation of Si–O phases and carbonyl groups were observed.

Synthesis and characterization of novel fluorinated poly(ether imide)s containing pyridine and/or phenylphosphine oxide moieties

4-(4-Trifluoromethylphenyl)-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine (9FPBAPP), as a new aromatic diamine, was prepared by a modified Chichibabin reaction of 4-(4-nitro-2-trifluoromethylphenoxy)acetophenone with 4-triflouromethylbenzaldehyde, followed by a catalytic reduction. A series of fluorinated poly(ether imide)s containing pyridine and/or phenylphosphine oxide moieties were prepared from bis(3-aminophenyl)phenylphosphine oxide (BAPPO), 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), and 9FPBAPP via a conventional two-step thermal imidization procedure with various mole ratios of BAPPO and 9FPBAPP. All the polymers were amorphous and soluble in common organic solvents such as N, N-dimethylacetamide and N-methyl-2-pyrrolidone and had Tg’s of 277–285°C, 5% weight loss temperature of 521–550°C in nitrogen. Furthermore, high char yields and good limited oxygen index values indicated that these polymers exhibited good thermal stability and flame-retardant property. Tough and flexible polymer films also had good mechanical properties with tensile strengths of 75–99 MPa, tensile moduli of 1.1–1.6 GPa, and elongations at break of 12%–24% and low dielectric constants of 2.81–3.53 (1 MHz), as well as high optical transparency with the ultraviolet cutoff wavelength in the range of 350–384 nm.

Synthesis and properties of (A2+B4)-type hyperbranched polyimides with different terminal groups

To investigate the effect of terminal groups on the properties of hyperbranched polyimides (HBPIs) for potential optical applications, a series of HBPIs bearing different terminal groups have been synthesized through a novel aromatic CF3-containing tetra-amine, 4,4′-di[3,5-di(2-trifluoromethyl-4-aminophenoxy)phenoxy] sulfone, and a long chain dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane, via a two-step polycondensation procedure. The synthesized HBPIs could form flexible and tough polyimide (PI) films, which exhibit good thermal stability with the glass transition temperatures of 191–234°C for differential scanning calorimetry measurement, the 5% weight loss temperatures of 533–610°C, and residual weights of 45.8–58.6% at 800°C under nitrogen atmosphere. The PI films have favorable mechanical properties with tensile strengths of 77–92 MPa, elongation at break of 3.55–7.99%, and initial modulus of 2.05–2.86 GPa. The films also exhibit the good transmittance of higher than 80% at 800 nm. The average refractive indices ( nav) and in-plane/out-of-plane birefringence (Δ n) measured at 632.8 nm are in the range of 1.5539–1.6022 and 0.0065–0.0077, respectively. The good transmittance in the visible region, tunable nav, and low Δ n are very suitable for optical applications.

Synthesis and properties of hyperbranched polyimides derived from tetra-amine and long-chain aromatic dianhydrides

The synthesized hyperbranched polyimides obtained from a novel tetra-amine have a treelike randomly branched topology with a branch-on-branch structure, which affords a compact, globular molecule.

Synthesis and characterization of ternary copolyimides derived from aromatic dianhydride and aromatic diisocyanates

A series of polyimide (PI) copolymers were synthesized via a one-step polycondensation procedure from benzophenone-3,3′,4,4′-tetracarboxylic acid dianhydride, toluene diisocyanate (TDI), and 4,4′-methylene bis(phenyl isocyanate) (MDI) with various mole ratios of TDI and MDI ranging from 70:30 to 100:0. The inherent viscosities of the resulting PIs were in the range of 0.51–0.80 dL g−1. The prepared PIs showed good solubility in common organic as well as in less polar solvents. All copolymers afforded tough and flexible films that had good thermal stability with glass transition temperature of 308–325°C and the temperatures of 5% weight loss in air and nitrogen being 420 and 460°C, respectively. The resultant PI films with thickness about 15 μm exhibited high transparency (>88%) in visible region (400–700 nm). Also, the cured PI films possessed good mechanical properties with tensile strength of 60.52–69.31 MPa and tensile modulus of 0.98–1.30 GPa.

Synthesis and characterization of novel fluorosilicone polyimides with high optical transparency

To overcome insoluble and low transmittance of the traditional polyimides (PIs), two kinds of novel fluorosilicone PIs were prepared. First, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene, compound 3a, and 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl ether, compound (3b), with 2-chloro-5-nitrobenzotrifluoride and p-hydroquinone or 4,4′-dihydroxydiphenyl ether were prepared. Second, hydrosilylation of nadic anhydride (NA) with 1,1,3,3-tetramethyldisiloxane (TMDS) yielded 5,5′-(1,1,3,3-tetramethyl-1,3-disiloxanediyl) bisnorbornane-2,3-dicarboxylic anhydride, compound (4). Initially, the conditions of the synthesis reaction such as reaction temperature, catalyst dosage, molar ratio of TMDS/NA, and reaction time on yield of compound 4 by the single factor approach were studied. The optimal reaction conditions were reaction temperature: 90°C, catalyst dosage: 1 ml (Pt% = 0.37%), molar ratio of TMDS/NA: 1/1.8, and reaction time: 3 h. The yield was 74.6%. Finally, two kinds of new organosoluble, light-colored, and good thermal stable fluorosilicone PI compounds (5a-5b) were synthesized from compounds 3a-3b and 4 and 4,4′-hexafluoroisopropylidenediphthalic anhydride), prepared through a typical two-step polymerization method. The solubility of the novel fluorosilicone PI films of compounds 5a-5b and the traditional PI film (4,4′-diaminodiphenyl ether (ODA)-biphenyltetracarboxylic dianhydride, DIY) were contrasted. The result showed that the fluorosilicone PI films have good solubility. These PIs were soluble in amide polar solvents and even in less polar solvents. The glass transition temperatures of compounds 5a-5b were 229.1 and 186.7°C and the 5% and 10% weight-loss temperatures were 519.8°C and 539°C, respectively. These films had cutoff wavelengths of 331.8 and 318.6 nm. Due to these properties, these PIs could be used as aerospace, photoelectric, and microelectronic materials.